Electrophotographic charging easel

ABSTRACT

A device for retaining a piece of electrostatic sheet material in multiple and replaceable registry with a projected image and including manually movable apparatus, movable over the registered sheet material, for placing a uniform electrical charge on the photoconductive coating of the sheet material.

United States Patent Wright, Jr. et al. 1451 Aug. 22, 1972 [54] ELECTROPHOTOGRAPHIC [56] References Cited 72 [CHARGING 2 5 UNITED STATES PATENTS t W ht Wh l 1 $1, 35,, 'gf y ggg 351 3; 3,322,098 5/1967 Pegram ..355/3 x "L 2,478,314 8/1949 Petty ..355/72 X 2,418,226 4/1947 Haff ..355/75 1 Assignccr n p 1119-, Norlhbmok, 3,549,251 12/1970 Olden ..355/3 122 May g 7 3,067,666 12/1962 Coffman .33/l84.5 X

[21 Appl. No.: 38,433 Primary ExaminerSamuel S. Matthews R I ted us A D ta Assistant Examiner-Kenneth C. Hutchison pplcalon a Attorney-Olsom'l'rexler,Walters& Bushnell [63] Contmua'uon-m-part of Ser; No. 877,405, Nov.

17, 1969, abandoned. 57 ABSTRACT 52 US. (:1 ..355/3, 355 72 A device for retaining a Piece of electrostatic Sheet 511 Int. Cl. ..G03g /02, G03b 27/58 material in multiple and replaceable registry with a 58 Field of Search ..355/3-17, 72; projected image a including manually movable 33 1 4 5 paratus, movable over the registered sheet material, for placing a uniform electrical charge on the photoconductive coating of the sheet material.

Claims, 15 Drawing Figures ELECTROPHOTOGRAPHIC CHARGING EASEL This case is a continuation-in-part of the US. Pat. Application Ser. No. 877,405, filed Nov. 17, 1969, now abandoned, entitled Electrophotographic Charging Easel.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrophotographic reproduction and more specifically to a device for posi tioning and electrostatically charging a piece of photoconductively coated sheet material.

2. Prior Art Electrophotographic printing of the type to which this application is directed is accomplished by exposing an image on a piece of electrostatically charged photoconductively coated sheet material. The exposure reduces or dissipates the charge to define latent image areas. Thereafter, the sheet material is immersed in a developing solution or toner to print the latent image.

The electrostatic charge on the coated sheet material, usually paper, is applied by a charging device of the corona discharge type which, when moved relative to the coated face of the photoconductive paper, will create a uniform electrostatic charge thereon.

In most prior art electrophotographic patents, such as the patent to S. W. Levine et al., US. Pat. No. 3,420,151, the charging is done automatically by machine and involves moving a coated sheet or web past a stationary charging device. Thus, the prior art usually required complicated, expensive automated machinery which is not readily adaptable to home or commercial darkroom use and which requires a great deal of adjustment for experimental usage.

It is to be understood that as used herein, the terms print, tone," or develop" refer to the same step.

In experimental electrophotographic printing, it may be desirable to charge, expose, print or tone and thereafter re-charge, re-expose and re-print or re-tone the same photoconductive sheet with the same image in registry. In multi-color printing, the same sheet must be re-charged, re-exposed and reprinted a plurality of times with different optically filtered portions of the original image being exposed on the sheet in registry with prior exposed and developed images. A number of prior art patents have been devoted to the problem of registry of successive exposures with the original exposure. Such prior art patents have usually been directed to obtaining this result automatically by complex machinery. Again, such systems are ill adapted to experimental work or to home or commercial darkroom usage.

SUMMARY OF THE INVENTION The present invention provides an economical charging and registry device which is particularly adapted for manual electrophotographic printing systems, and which is ideally usable for experimental developing or home or commercial darkrooms where only a single or small number of prints from an original are required. The device includes a base member which has associated therewith means for registering a piece of photoconductive sheet material thereon in such a manner that it may be removed and replaced in substantially the same position. Preferably attached to the base member is a power supply and a movable corona discharge charging arm, which may be manually moved over the sheet of photoconductive sheet material to provide an electrophotostatic charge thereon. The power supply may be attached to the base member either by directly mounting it thereon or by incorporating it as a part of the movable charging arm.

The base member is preferably a metal or metal sheathed, grounded, rectangular board which has a top side having linearly spaced registering pins projecting therefrom. The base member also preferably has a series of linearly spaced slots adjacent one edge thereof. The slots have excavated cavities thereunder, and provide a hinged attachment point for a masking member. The masking member includes a rectangular frame for overlying and defining the marginal portions of a photoconductive sheet positioned on the base member. The masking member has a series of dimensioned spaced holes in one margin thereof which are adapted to mate with the pins to position the masking member. Registration of the photoconductive sheet is accomplished by providing dimensioned holes adjacent one edge of the sheet which mate with the pins.

The sheet can therefore be laid atop the base member with the pins projecting through the holes in the sheet to accurately register the sheet a plurality of times. The hinged masking member is then placed atop the sheet in registry with the pins to define a portion of the sheet to be charged and on which the image is to be projected.

The charging member includes a power supply and a transverse arm providing a shield for transversely extending wires. The transverse arm extends from one edge of the base member to the other and is mounted on antifriction insulators adapted to slide along the marginal edges of the base member so as to move the arm longitudinally of the base member. The bottom of the arm is spaced from the top of the base member a distance sufficient to clear the projecting pins and masking member. The wires of the shield member are connected by an electrical cord to the power supply. Energizing the power supply will create an electric current in the transverse wires of the arm, producing a corona discharge between the wires, shield, and grounded base member. Thereafter, moving the arm over the photoconductive paper in relative darkness will place a static electric charge on the coated face of the paper.

After the paper has been charged, the arm can be slid to one end of the base member out of the way, where it will not interfere with projection of an image from a projecting source onto the charged paper. In one embodiment, the power supply is attached to the base member in cantilever fashion with the bottom of the power supply overlying in spaced relation a portion of the top of the base member at the back thereof. The arm is dimensioned to be positionable under the power supply and a contact switch depends from the power supply in a position where it will be activated by contact with the arm. The contact switch turns off the power supply when the arm is positioned at the rear of the base member.

In another embodiment, the power supply is attached to a part of the arm and controlling switches for the power supply are provided on the transverse arm.

The base member defines both a registering easel for the photoconductive paper and a mounting member for a charging device. The base member is preferably adapted to be used in a defined position relative to a projecting device so that the focal point of the projecting device will correspond to the top of the base member. Thus, the base member will be allowed to remain in position with respect to the projector while the photoconductive paper can be removed therefrom for development and later be replaced thereon in exact registry with the projected image.

Although the charging easel of this invention will be described in its preferred embodiment, primarily for use with a transparency projector preferably of the photographic enlarger type, it will be understood that the device is equally usable with an opaque projector or a contact printer. In the latter case, the contact printer should be equipped with a registering means akin to the registering means of the easel whereby a re-charged sheet of photoconductive material can be re-registered in association with the contact printer and image.

It is therefore an object of this invention to provide an inexpensive device which provides for multiple reregistry of a sheet of photoconductively coated material with respect to a projected image.

It is another and more important object of this invention to provide a combined device for repeatedly registering a photoconductively coated paper with respect to a projected image and for placing a static electric charge on the paper.

It is a further and more specific object of this invention to provide an electrophotographic charging easel which includes a base member having means thereon for repeatedly registering a sheet of photoconductively coated material with respect to a projected image and for providing said sheet with an electrostatic charge by manually moving a corona discharge device associated with the easel across the face of the photoconductively coated sheet material.

It is yet another and specific object of this invention to provide an electrophotographic charging easel which includes a base member having means thereon for repeatedly registering a sheet of photoconductive material with respect to a given position and which has mounted thereon a movable charging arm equipped with a power supply and means for creating a corona discharge, the arm being movable across the photocon' ductively coated material received on the base member.

It is another and specific object of this invention to provide an electrophotographic charging easel including a base member for receiving a sheet of photoconductively coated material, the base member having associated therewith a movable charging arm for creating a corona discharge to charge the photoconductively coated material, the arm including a controlled power supply and switch means for activating the corona discharge.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of a certain preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel I concepts of the disclosure, and in which:

FIG. I is a perspective view of the electrophotographic charging easel of this invention in position with respect to an enlarger projecting device;

FIG. 2 is a perspective view of the charging device of FIG. I, equipped with a larger mask;

FIG. 3 is a stop plan view of the charging easel of FIG. 1 illustrating movement of the transverse arm;

FIG. 4 is a view similar to FIG. 3, illustrating the charging arm in its stored position;

FIG. 5 is top cross-sectional view taken along the lines VV of FIG. 2;

FIG. 6 is a cross-sectional view taken along the lines VIVI of FIG. 3;

FIGS. 7, 8 and 9 are schematic views illustrating in block diagrams use of the charging easel of this invention with opaque and transparency projectors, and a contact printer;

FIG. 10 is a perspective view of a preferred embodiment of this invention with the power supply contained in the movable arm;

FIG. 11 is a fragmentary cross-sectional view of the embodiment of FIG. 10;

FIG. 12 is a fragmentary longitudinal cross-sectional view of the embodiment of FIGS. 10 and 11;

FIG. 13 is a top plan view partially in section of the embodiment of FIGS. 10 through 12, with underlying features illustrated by broken lines;

FIG. 14 is a modified schematic of the electrical circuitry of the preferred embodiment of FIG. 10; and

FIG. 15 is a partially exploded view illustrative of the combination insulating slides and corona wire holders of the embodiment of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT Electrophotograhic printing of the type done in connection with the use of the equipment of our invention involves the development of an image from an original on a photoconductively coated piece of sheet material. The sheet material is a conductive member, usually paper, which may have a rag or other fiber content. Alternatively, the sheet material may be plastic or glass, preferably with a conductive coating or bulk conductivity characteristics and which has a coating of photoconductive insulating material thereon. The coating is generally a zinc oxide with a resin binder wherein both the oxide and binder have been chosen to give the coating the desired sensitivity and contrast values. Alternatively, organic photoconductors or photoconductive pigments other than zinc oxide may also be used.

The photoconductive coating is generally of the type which, in the dark, has a high electrical resistance comparable to that of insulating material and which is therefore able to retain an electrostatic charge. When the layer is exposed to light, its electrical conductivity is increased in the illuminated area so that the electrostatic charge may be reduced or dissipated through the conductive sheet material.

The image to be printed is developed by first charging the photoconductively coated sheet material with a uniform elecnostatic charge; second, projecting the desired image on the coating to reduce or dissipate portions of the charge, and third, developing the resultant latent image by depositing various amounts of pigmentation on the exposed photoconductively coated sheet material in areas and proportions determined by the charge remaining on portions of the coated sheet material.

In black and white reproduction, such as is common in office copying machines, the above may be accomplished with one charging step. However, in experimental printing it may be desired to create special effects which will require multiple successive charging and exposing steps with the same or a different image being exposed. In such cases it is necessary to reposition the sheet material with respect to the focal plane of the projected image with a high degree of accuracy. If the same image is to be re-exposed it is desirable that it be in complete registry with the prior exposed and printed image. In multicolor printing, where a different optically filtered portion of the original image is exposed in successive charge-expose-develop sequences, it is necessary that the registry be accomplished as accurately as possible without unduly inconveniencing the operator.

Our invention provides a base member which has means thereon for accurately re-registering a piece of sheet material a plurality of times with respect to the stationary base member. This allows the sheet material to be exposed on the base member and thereafter be removed therefrom for developing in a different area. The developed sheet material can then be replaced on the base member in the same position it occupied when originally exposed. Since the base member is stationary, it can be located in a given position with respect to the focal plane of the projected image. Therefore, definitely registering the sheet material with respect to the base member will result in registry of the sheet material with respect to the projected image.

The photoconductive coating is charged with an electrostatic charge by moving it through an electric corona discharge in the darkness. Methods of producing the electrostatic field necessary to effectuate the placement of the charge on the photoconductive coating are old in the art. Basically what is required is a controlled power supply and a plurality of spaced-apart parallel wires connected to the power source adapted to be spaced from the coated side of the sheet material in a manner such that the field may be moved with respect to the photoconductively coated surface to impart a charge thereto.

Inasmuch as the photoconductive coating will retain the electrostatic charge only in the absence of light or similar radiation, it is necessary for the sheet material to be charged in darkness. The charged sheet must then remain in darkness until after the image has been exposed and developed.

Our invention provides, in combination with the base member and registry means, a manually movable charging arm which is adapted to be moved across the coated sheet while the latter is positioned on the base member. The charging arm and power supply therefore are mounted in association with the base member so as to be conveniently usable therewith in darkness.

For purposes of this specification, the charging easel will be described as being used in connection with a standard darkroom enlarger which is mounted with respect to the easel so as to project the focal plane of the original image on the top surface of the base member. It is to be understood that the use of an enlarger is optional and any device capable of projecting a focused image onto the base member such as a standard projector or opaque projector may be utilized.

FIG. 1 illustrates the easel 10 of our invention positioned on top of a table 11 which serves as a mount for an enlarger 12. The enlarger is mounted by means of a bracket 13 attached to substantially vertically extend ing beams 14 which are fastened to the table 11 adjacent the rear 15 thereof. Brace members 16 serve to retain the enlarger in the upright position. The enlarger is vertically movable with respect to the top 17 of the table 11 and has controls 18 for adjusting the focal plane of the image projected through the lens system 19. A light from a source 20 may then be projected through a transparency mounted behind the lens system 19 to project an image through the lens system into focus at any desired point below the enlarger.

The charging easel 10 includes a base member 21, registering means 22, masking member 23, a power supply 24 and a transverse charging arm 25 mounted on the base 21.

The base member 21 may be metal or as illustrated in FIG. 6 may be composed of a layer of material other than metal such as wood which has a metal sheathing 31 at the top and along the sides. A high frictional material such as foam rubber 32 or the like may be attached to the bottom of the non-metal layer 30 to prevent shifting of the base member 21 when placed on the top 17 of the table 11. The metal sheathing of the base member is grounded as at 33. The top surface 34 of the base member 21 is flat and preferably level so that it may be placed co-planar with the focal plane of the projected image.

The registry means 22 comprises a plurality of spaced apart pins 35 which project vertically from the top 34 of the base member 21. The pins 35 are aligned and extend transversely across the base member in a plane spaced from the back 36 of the base member a distance sufficient to provide storage clearance for the transverse arm 25 and the power supply 24 as illustrated in FIG. 4. The pins 35 are dimensioned to mate with equally sized and spaced holes in the photoconductively coated sheet material 37. The holes in the sheet material extend in spaced relation along one edge thereof. It can therefore be seen that by placing the sheet upon the top 34 of the base member 21 with the pins 35 projecting through the holes the sheet will be retained in a given position with respect to the base member. Thereafter, the sheet may be removed by lifting it off the base member and be replaced in the same position by re-aligning it with the pins. Thus, the pins 35 cooperate with the spaced dimensioned holes in the sheet material to provide a registry means whereby the sheet may be replaced in the same position on the base member a plurality of times. Inasmuch as the base member is positioned in a given spot with respect to the optically projected image, registering of the sheet material with respect to the base member results in registry of the sheet material with respect to the projected image. In those instances when the sheet is coated on one side only, the registry means also assures that the sheet is always face up. Varying the spacing of the registry pins 35 from one another or from the end and using two or more pins and complementarily sized holes to effect registry results in a system where it is impossible to place the paper on the base member in the respective area in a face down position. Attempting to place the sheet in registry with the coated side face down would result in the sheet extending to the wrong side of the line of pins. It is to be understood that the particular embodiment of the registry means herein described involving the use of projecting pins and complementarily dimensioned holes in the sheet material is a preferred embodiment only. Other registry means may be utilized such as spaced apart right angle clamps and/or aligning grid lines. Another method of assuring that the paper is placed on the base member in a predetermined position with the coated side face up, is to employ different shaped pins with, for example, one pin being rectangular and another square or triangular, etc.

It is further to be understood that any number of spaced apart pins and complementarily dimensioned holes may be utilized. Sheets of various sized materials may also be used with a base member having any given number of projecting pins 35. FIGS. 2, 3 and 4 illustrate various sized sheets being utilized. In FIG. 3, a sheet which is longer than it is wide is illustrated with three of four illustrated pins projecting through the paper. FIG. 4 illustrates a sheet which is wider than it is long, which also has three of four pins projecting through to obtain registry. FIG. 2 illustrates a larger sized sheet which has all four pins projecting through the sheet. It is to be understood that any number of pins may be utilized, two being sufficient to obtain registry. It is also to be understood that although the pins have been described as standing in a line transverse to the base member and spaced from the top 36 they may be positioned in different configurations, as for example, in a line extending longitudinally of the base member spaced from one of the sides.

It is desirable to image less than the entirety of the sheet material so as to provide an unprinted margin around the periphery of the printed image. When this is done, the holes which combine with the pins for registry can be provided in the marginal portion so as not to detract from the printed image. Additionally, the paper may be dimensioned so as to provide a larger margin along the edge which carries the registry holes. Further, a strip of the edge may be provided with perforations or the like to create a tear strip easily removable from the remainder of the paper, which strip will have the registry holes therethrough.

Our invention provides a masking member 23 for defining this peripheral margin. The masking member 23 comprises a metallic frame 40 which is dimensioned to overlie the sheet material 37. The metal frame 40 is a rectangular hollow member which when positioned on top of the sheet material 37 will cover the portions of the sheet material adjacent the peripheral edges thereof.

In the preferred embodiment the masking member 23 has slots 42 along one edge thereof. The slots 42 are dimensioned and spaced so as to mate with the pins 35. Therefore the masking member 23 can be registered, in the same manner as the sheet material 37 with the base member 21. In this manner, the masking member may be removed from the sheet material 37 a plurality of times and be replaced in the same position so as to not change the imaged boundary on plural charge-exposedevelop sequence prints. In the preferred embodiment, the slots have a width approximately equal to the diameter of the pins but a length which is greater than the diameter so as to allow the masking member 23 to be easily pivotably swung downward. In this instance registry is effected by both the mating of the pins 35 and slots 42 and by tongues 47 which detachably attach the masking member to the base member.

A plurality of spaced apart slots 44 is provided through the metal sheathing 31 of the base member adjacent one side 45. The slots communicate to cavities 46 illustrated in FIG. 5 in the non-metal layer 30 underlying the sheathing 31. The metal frame 40 of the masking member 23 has a plurality of spaced apart tongues 47 along one marginal edge 48 thereof. The tongues are dimensioned and spaced so as'to project into the slots 44 to provide a hinge connection of the frame 40 to the base member 21. The tongues 47 and slots 44, as explained above, cooperate with the slots 42 and pins 35 to position the masking member with respect to the paper and base member 21.

The tongues 47 are integral with the main portion 49 of the frame 40 through an angled portion 50. The angled portion 50 is dimensioned as illustrated in FIG. 2 so as to project upwardly from the top 34 of the base member 21 in the direction of the side 45. The angled portion 50 terminates in the tongues 47 which extend downwardly therefrom through the slots 44 into the cavities 46. The tongues 47 and the cavities 46 are dimensioned so as to allow the tongues to freely swing through an arc in the cavity when the masking member is pivotally swung up from the end 52 remote from the tongues 47. The tongues 47 will abut the underside 53 of the metal sheathing 31 when the main portion 49 of the masking member has been swung upward and overcenter. This position is illustrated in FIG. 5 where it can be seen that the abutment of the tongue 47 with the underside 53 of the metal sheathing 31 will retain the masking member in an upright position.

The angled portion 50 provides an initial lift sufficient to raise the side 52 off of the top 34 of the base member a distance so as to be easily graspable by the fingers of the operator. It can be seen from FIG. 2 that a downward pressure on the angled portion 50, such as could be applied by the thumb of the operator, will cause the angled portion 50 to become planar with the top 34 of the base member 21. With the angled portion 50 planar with the top 34, the side 52 will be lifted off of the base member.

Charging of the coated sheet material 37 is accomplished by moving the transverse arm 25 longitudinally of the base member 21 over the face of the coated sheet material.

A controlled power source 24 may be mounted to the base member 21 along the edge 36 and is attached to an electric power outlet by wires 60. The power source 24 has an actuating switch 61 associated therewith and is connected to the transverse arm 25 by electrical wires 62. The power source is of the type which will develop a controlled electrical current as for example, of -6 K.V. d.c.

In the embodiment illustrated the power source 24 is fastened to the base member 21 in a cantilever fashion so that the bottom thereof 63 is spaced from the top 34 of the base member a distance sufficient for the transverse arm to be positioned under it. The transverse arm 25, as best illustrated in FIG. 2, extends across the width of the base member and projects beyond the side thereof a short distance.

In one embodiment, as best illustrated in FIG. 2, the power source 24 is attached to the base member in a cantilever fashion by a back wall member 95. Therefore, the bottom 96 of the power supply overlies a rear portion 97 of the top of the base member 21 in spaced vertical relation thereto. The transverse arm 25 is dimensioned so that it may be positioned at the rear 97 with a portion of the arm under the power supply. When the arm is so positioned, it will be out of the way of the paper 37 and masking member 23 so as to not interfere with image projection or with raising of the masking member or removal or insertion of the paper. The switch 61 acts as a primary off-on switch for the power supply. In one embodiment, a secondary contact switch 98 depends from the bottom 96 of the power source in a position where it will contact and be activated by the transverse arm 25 when that arm is in the storage position at the rear of the base member. The switch 98 is preferably wired in series with the switch 61 so that it will control whether the power supply is on or off in dependent response to the position of the transverse arm. This allows the corona discharge to be activated or deactivated by the operator simply by moving the transverse arm once the switch has been placed in the on position.

In another embodiment, the power supply 24 may be mounted on the top of the transverse arm 25 and moved therewith. In such an embodiment, the contact switch 98 would not be used but could be substituted by a switch attached to the electrical cord servicing the power supply and mounted adjacent the rear of the base member in a position to be activated by movement of the arm.

In a preferred embodiment, the power supply is constructed as a portion of the transverse arm and switches controlling activation of the power supply may be provided on the arm for activation by a person moving the arm.

As illustrated in FIG. 6, the arm 25 comprises a substantially right angle U-shaped metal member 65 with out-turned flanges 66 adjacent the open end. Insulating blocks 67 close the longitudinal ends of the U-shaped metal member and have a base portion 68 which extends beyond the flanges 66. The base portion 68 is L- shaped as illustrated in FIG. 2 with the bottom surface 69 of the short leg 70 of the L dimensioned to ride on top of the base member 21 at the peripheral side edges thereof. The inside edge face 72 of the long leg 73 of the L is adapted to contact the side walls of the base member 21 thereby accurately positioning the transverse arm 25 with respect to the base member.

As illustrated in FIG. 2, the top of the base member 21 may have a projecting edge illustrated at 99 which extends beyond the sides of the base member to provide an undercut shoulder. The edge 99 then cooperates with an alternative form 68b of the insulation block. The insulation block 68b has a groove 100 formed along the inside edge which mates with the projection 99 in a tongue and groove connection, as illustrated in the broken away portion in the upper lefthand side of FIG. 2. This results in firmly attaching the transverse arm 25 to the base member 21 in slidable relation therewith. To prevent the arm from being removed from the base member at the front and rear of the member, the metal sheathing may be carried past the side as at 101. Alternatively, abutment stops may be fastened to the sides.

The insulating member 67 is preferably constructed of a material which has both insulating and anti-friction properties such as Delrin, Teflon, Nylon (registered trademarks of E. I. du Pont de Nemours & Co.) or a polystyrene. The anti-friction properties of such materials allow the transverse am 25 to freely slide across the top 34 of the base member 21. The insulating blocks 69 are dimensioned so as to space the flanges 66 which define the bottom of the U-shaped metal members a distance from the top 34 of the base member 21 sufficient to clear both the registry pins 35 and the angle portion 50 of the mask. In this manner the transverse arm 25 can be slid the length of the base member 21 over the coated sheet material 37, pins 35 and masking member 23.

A plurality of transversely extending wires extend the length of the transverse arm 25 and are attached to the insulating blocks 67. The wires 80 are interconnected and are connected to the power supply through the electrical cord 62. The wires 80 are parallel and are preferably spaced apart approximately one-half inch. The wires preferably have a diameter of l to 3 mils and may be constructed of tungsten, stainless steel or the like. The wires 80 may be four in number and are spaced further apart from the sides of the U-shaped metal member than from one another.

Energization of the power supply by the switch 61 will result in a current flowing through the wires 80 when the arm is moved from the storage position. The current flow through the wires 80 will produce a corona discharge whose field will extend from the wires to the metal sheathing 31 of the base member. Moving this field over the photoconductively coated sheet material 37 by sliding the transverse arm 35 the length of the base member 21 will result in a uniform charge on the coating of, for example, 400 V. Positioning the transverse arm 25 to the rear of the base member 21 will activate the contact switch 98 to turn off the corona discharge.

The U-shaped metal member 65 of the transverse arm is preferably grounded to the metal casing of the power supply by ground wire such as illustrated at 90. The power supply 24 may be grounded by means of a three wire safety electrical connection with the wires 66.

The charging easel of our invention is designed to be used as follows. The base member with associated power supply and charging arm is positioned on top of a table 11 or other structure with respect to the enlarger or other projector so that the original image may be focused on the top 34 of the base member and paper. The positioning and size of the projected image may be accomplished either by moving the charging easel with respect to the projector or, in the case of the enlarger illustrated in FIG. 1, by adjusting the position of the enlarger with respect to the base member.

After the size of the printed image has been chosen and the projector positioned with respect to the base member and paper so as to project the desired sized image onto the paper in the area below the registry pins 35 and within the outlines of a correspondingly sized masking member 23, a masking member of suitable dimensions is positioned atop the coated sheet material with the tongues 47 projecting into the corresponding slots 44 and the pins 35 projecting into the corresponding slots 42. It is to be understood that the number of slots 42 and tongues 47 will be dependent upon the size of the masking member 23 chosen.

With the coated sheet 37 and masking member 23 thus positioned in registry with the focal point of the image to be projected, the sheet material is ready for charging and exposing.

Charging of the sheet material 37 must be accomplished in darkness and it is a feature of our invention that this may be easily done due to the fact that charging is accomplished with the sheet material already positioned in the image plane of the image to be projected. With the lights turned off the power supply 24 is activated by moving the wand to provide the corona discharge between the wires 80 and the metal sheathing 31. Thereafter the transverse arm 25 is manually slid along the length of the base member 21 over the coated sheet material 37 and masking member 23. The quality of the charge to be placed on the sheet material may vary by varying the duration of time which the sheet material is exposed to the corona discharge, and further depends upon the type of coating used on the sheet material. The presence of the masking member which is in contact with the grounded base member will prevent charging of the covered-over portions of the sheet material.

After the sheet 37 has been charged by sliding the transverse arm 25 over it one or more times, the power supply 24 is deactivated and the arm is moved to its storage position adjacent the end 36 as illustrated in FIG. 4. In this position the arm 25 is out of the way and does not overlie any portion of the sheet material 37 or masking member 23. In one embodiment, the power supply it automatically deactivated with the arm in the storage position by contact with the switch 98. The image is then exposed on the sheet material 37 by tuming on the enlarger 12 for a period of time as determined by the timer 93. This will create a latent electrostatic image on the coated surface of the sheet material by reducing or dissipating portions of the charge thereon in the manner hereinbefore described.

The sheet material 37 with the latent image thereon may then be removed from the base member 21 by pressing down on the angle portion 50 of the masking member to lift the edge 52 off of the base member. Thereafter moving the masking member to the position illustrated in FIG. will allow access to the edge of the sheet material on top of the base member. The sheet material is then lifted off of the base member and can be removed to a developing station. If it is desired to reexpose the same piece of sheet material with the same image as previously exposed to correct mistakes of exposure or development or for special effects or for a different optically filtered portion of the original image, as in the case of multi-color printing, the sheet material may be repositioned, in the light, on the top 34 of the base member in the same position that it previously had due to the presence of the registry means. Further, the cooperation of the masking member 23 with the registry means 22 will result in the mask frame being positioned atop the sheet material 37 in the same position which is previously obtained. Thereafter the lights may be extinguished and the sheet material charged and exposed in the previously described manner.

FIGS. 7, 8 and 9 schematically illustrate with block diagrams the charging easel of this invention may be used with any device capable of exposing an image on the charged paper. In FIG. 7, the easel is used as mentioned above to create an electrostatic charge on the photoconductively coated sheet material. Thereafter, the sheet is exposed to an image projected by an opaque projector. After exposure, the image is printed in the normal fashion. FIG. 8 is a view similar to FIG. 7 illustrating the sequential steps of printing from a transparency by means of a transparency projector such as is illustrated in FIG. 1. FIG. 9 sequentially illustrates the same steps in connection with a contact printer. When using a contact printer in connection with the charging easel of this invention, the contact printer should be equipped with registering means such as the spacedapart pins disclosed above.

FIG. 10 is a perspective view of a preferred embodiment for the charging easel of this invention.

The preferred embodiment easel has a base member 111 constructed of top 112 and bottom 113 U- shaped cross-section metal plates. The plates are assembled in face-to-face opposed inverted relation with the side walls at right angles to one another. An insulating spacer means may be positioned between the two plates and fastened thereto to provide assembly of the base member. The upper base plate 112 is preferably assembled with its legs 114 at the longitudinal ends of the base member 111 whereby relatively thin edges 115 are provided at the sides of the top of the base extending the length of the base member 111. The edges 115 then terminate in the down-turned legs 114. The top base member 112 is dimensioned with respect to the bottom base member 113 so as to provide a gap 116 between the edges 115 and the tops 117 of the legs 118 of the bottom plate 1 13. The edges 1 14 act as abutment stops for glide blocks and 131 and 134 and to prevent the arm from sliding off the ends of the top plate 112. The top plate 112 has a plurality of slots 119 therethrough adjacent one side thereof to receive the tongues of the masking member 23. A plurality of holes 120 are also provided transversely across the plate 112 to receive the pins 35 which may be individual or which may be protruberances on a strip fastened to the underside of the plate 1 12 with the protruberances projecting through the openings 120 to provide the alignment means pins 35.

Mounted atop the base member 111 is a transverse movable arm 122 which carries the power supply, switching means, and corona discharge wires.

As best illustrated in FIGS. 11 and 12, the transverse arm 122 includes a U-shaped cross-section metal base member or shield 123 which extends transversely across the base member 111 of the charging easel. A second U-shaped metal member 124 is centrally positioned in the bight of the member 123 and extends substantially the length thereof, thereby separating the interior of the member 123 into three semi-enclosed chambers 125, 126 and 127 extending the length of the member 123. The corona discharge wire 128 is strung through the openings 125, 126 and 127 with one parallel span positioned in each of the open chambers separated from one another by the walls of the U- shaped member 124.

Insulating members 130 and 131 close the longitudinal ends of the member 123 and provide anchoring means for the wire 128. The insulating blocks 130 and 131 have bottom surfaces 132 and 133 which rest on the top surface of the top plate 112 adjacent the edges 1 to provide a glide support for the member 123.

Also associated with the insulating blocks 130 and 131 are substantially J-shaped insulating blocks 134 and 135. The blocks 134 and 135 are attached to the outer sides of the blocks 130 and 131 along the inner face of the long leg of the J with the top surfaces 136 and 137 of the short legs 134b and 135k in spaced relation to the glide surfaces 132 and 133 and underlying them, thereby providing grooves in the insulation block assemblies. The edges 115 of the top plate 112 are received in the grooves and the insulating blocks 134 and 135 are securely fastened to the blocks 130 and 131 thereby firmly mounting the shield base member 123 to the base member 111 with the bottom of the member 123 spaced a given distance from the top of the plate 112.

Mounted atop the shield 123 is a bracket member 138 having side legs 139 mounted to the shield supporting a cross member 140 which extends substantially the length of the shield. The member 140 has a central section 141 which is slightly higher than the portions to either side thereof. The controlled power supply 142 is mounted beneath the central section 141, attached thereto as by means of screws or the like. A power supply off-on switch 143 is attached to the member 140 on the top thereof adjacent the central section 141 and has a spring-urged contact 144 extending therefrom in the direction of the central section 141. A power on indicator light 145 is also attached to the member 140 adjacent one side thereof with the bulb 146 projecting above the bracket. On the other side of the member 140, a corona discharge on indicator light 147 is mounted to the bracket with the bulb 148 thereof projecting above the bracket.

A housing member 150 is received over the bracket support and defines partial front 151, back 152 and side 153, 154 walls enclosing the shield 123, bracket 140 and power supply 142. The housing 150 has a large centrally disposed opening in the top thereof providing access to the top of the bracket 140 and to the switch 143 and lights 145 and 147. The housing 150 further has the central portions of the front 151 and back 152 faces cut away in communication with the top opening 155 as at 156 and 157. The front and back sides 151 and 152 are inturned at the openings 156 and 157, thereby providing ledges 158 and 159 which extend a short distance towards one another, terminating in spaced relation to the power supply 142.

A press switch 160, best illustrated in FIG. 13, is centrally positioned atop the support portion 141 and has side flanges 161 and 162 disposed in the open portions 156 and 157 and accessible therethrough. The top portions 163 and 164 of the switch 160 which are integral with the flanges 161 and 162 are spaced apart by a central gap 165 closed at either end by integral plastic loops 166. The loops 166 are constructed of resilient material such that when the flanges 161 and 162 are pressed towards one another, the loops 166 are deformed, allowing the portions 163 and 164 to move towards one another narrowing the gap 165. When pressure on the flanges is removed, the resilient nature of the material of the loops 166 will cause the portions 163 and 164 to return to their normal spaced-apart position.

Lugs 167 are positioned on the underside of the top portions 163 and 164 and are integral therewith. The lugs are positioned two to a portion adjacent either end thereof and terminate adjacent the central gap 165 in pointed ends 168 providing sloping abutment shoulders 169. A slide bar 170 is positioned beneath the switch member 160 and atop a power supply 142 where it may be retained by a key and slot or other device as indicated at 171. The slide bar 171) is longitudinally movable towards and away from the off-on switch 143. When urged towards the switch 143, the end 172 of the slide bar 170 will actuate the contact 144, thereby tuming on the power supply. Flanges 173 project from either side of the slide bar 170 at positions adjacent the lugs 167. The flanges 173 have sloping faces 174 adapted to be contacted by the abutment shoulders 169 in a wedge fashion. In this manner, when the flanges 161 or 162 of the switch 160 are depressed, the abutment faces 169 of the lugs 167 will engage the sloping faces 174 of the slide 170 to move it in the direction of the switch 143. It can be seen that this will occur if both of the flanges 161 and 162 are squeezed towards one another or if only one flange is urged towards the center of the arm 122. It is contemplated that in some instances the spring force of the contact 144 will be sufficient to move the slide bar back to its neutral position when pressure is released on the flanges 161 and 162. In other instances, it may be desirable to incorporate a return spring.

The top and longitudinal end walls of the arm 122 are defined by a housing strap which is substantially U-shaped and which is positioned over the top of the housing member 154 and the switch 160. The housing strap has two openings 181 therein through the top thereof positioned to overlie the indicator lamps 146 and 148. Translucent colored inserts 182 may be positioned in the openings 181 to indicate when the lamps are lit with different colors. The housing strap is fastened to the outside ends of the J-shaped blocks 134 and 135 either by screws or by indexing projections on the blocks 134 and 135 either by screws or by indexing projections on the blocks with openings through the strap. In this manner, the transverse arm 122 is firmly attached to the blocks 134 and 135 which together with the blocks 130 and 131 provide insulating glides and attachment members movably attaching the arm 122 to the top plate 1 12 for slidable movement therealong.

Electrical connection to the power supply 142 and to the corona wires 128 is provided through an opening in the back wall 191 of the base member giving access to the space between the bottom 113 and top 114 members for a three-line grounded power cord 194.

As illustrated in FIG. 13, a pair of spacer members 195 is positioned between the bottom 113 and top 114 diverging at a relative angle from one another across the width of the base member 111. The convergent ends 196 of the spacers 195 terminate in spaced relation to one another substantially more than half-way across the width of the base member 111 from the divergent ends 197 thereby providing an open-ended triangular shaped space therebetween in the area between the top 112 and bottom 113 of the base member. The power cord 194 is fastened by a holddown member 198 adjacent the throat of the triangular space exterior thereof. Prior to passing through the hold-down member 198, the ground wire 199 of the cord 194 is grounded to a Z-shaped plate 200 fastened to the top plate 112 of the base member 111 thereby grounding the top plate 112. Thereafter, the three wires of the cord 194 project into the triangular space defined by the spacing members 195 and extend to the J-shaped block 135 at one end of the transverse arm 122. The block 135 has a channel in its outer wall for receiving the wires of the power cord 194 and threading them upwardly to the space between the housing strap 180 and the housing member 150. A tightenable hold-down bracket 201 on the bottom of the J-shaped block 135 serves to fasten the wires 194 to the block. Thereafter, they are threaded under the housing member and thence inwardly to the indicator lamps, switch, power supply, and ground.

The provision of the open ended triangular space works as a safety feature giving the power cord flexing room to accommodate movement of the arm while retaining the cord in a given space between the top 112 and bottom 113 plates of the base member. This way, the power cord is never exterior of the charging easel during movement of the charging arm. The hold-down member 198 functions as a pivot point.

FIG. 14 generally indicates the wiring of the preferred embodiment of the invention. The power cord 194 consists of current-carrying wires 203 and 204 and the ground wire 199. As is indicated, the ground wire 199 is first grounded to the top plate 112 at the Z-shaped bar 200, and then to the bracket member 138 and shield 123. The wire 203 is attached to the switch 143 and through the wire 205 to the lamp 145. The switch 143 has its other contact attached through the wire 206 to an input bracket 210 on the power supply 142. The lamp 145 has its other contact attached through the wire 205 to an input bracket 211 on the power supply 142. The wire 204 is attached to the bracket 211 in this way completing a circuit to light the indicator lamp 145 to indicate that power is supplied to the transverse arm, the circuit being the wires 203, 205, 207, the bracket 211 and the wire 204. A wire 208 is attached to the wire 207 and terminates in the indicator lamp 147. The other contact of the lamp 147 is attached to the wire 209 which in turn is attached to the bracket 210. When the switch 143 is closed, communicating the line 203 to the line 206, the indicator lamp 147 will be lit to indicate that the power supply is turned on. The circuit comprises the line 203, the switch 143, the line 206, the bracket 210, the line 209, the indicator lamp 147, the line 208, the line 207, the bracket 211, and the line 2. Activation of the switch 143 therefore energizes the power supply 142 by closing the circuit to the bracket 210. The output from the power supply 142 is by way of the line 213 which extends to the corona wire 128.

The insulating block 130 has a depression 220 therein, in which is fitted a metallic anchor body 221 having a tab 222 projecting from one end thereof. The press clip end 223 of the line 213 from the power supply is attached to the tab 222 thereby energizing the metallic anchor member 221. The corona wire 128 is attached to one end of the anchor bar 221 adjacent the tab 222 by means of a tensioning spring 224. From there it extends through the channel to the insulating block 131 which has a U-shaped depression 226 therein having a centrally raised portion 227 in the bottom thereof. The raised portion has inwardly and downwardly slanting side walls 228 and the corona wire 128 is passed around the centrally raised portion 227 in the space between the side walls 228 and the back wall 229 of the U-shaped depression. The corona wire exits from the other side of the depression in line with the center of the channel 126. Tensioning the corona wire will urge the wire against the inwardly and downwardly slanting side walls 228 to retain the corona wire in place around the centrally raised bottom 227. Thereafter, the wire 128 extends back to the block 130 where it passes around an anchor tang 230 on the anchor bar 221 which is aligned with the center of the channel 126. The wire then passes around a second tang 231 aligned with the center of the channel 127 and thence back to the block 131 where it is anchored as at 232. Because the blocks v130 and 131 are constructed of insulating material, it can be seen that energization of the power supply will energize the wire 128 to create a corona discharge between the wire and the grounded shield 123 and the grounded top plate 112.

Thereafter, moving the transverse arm across the base member 111 will energize the photoconductive coating of a piece of sheet material received on the base member 111. The mask 23 is normally grounded by contact with the grounded base plate 112. However, in order to insure grounding of the masking member 23 when relatively thick sheet material is used, a spring ground member 235 best illustrated in FIG. 11 is attached to the Z-shaped plate 200 and has a portion 236 extending outwardly therefrom in the area underlying the slots 119 through which the tongues 47 of the masking member 23 project. The tongues contact the portion 236 and are grounded therethrough to the Z- shaped member 200 and the ground wire 199. Due to the spring nature of the ground member 235, movement of the mask in raising or lowering it will merely cause a bending of the member 236 while retaining grounding contact.

By arranging the spacing of the slots 119 and tongues of the mask 23, it can be assured that a mask of a given size is placeable only in a defined area. For example, if the two slots closest to the normal top of the base member are spaced apart with a given spacing and thereafter the spacing between the slots increases, it will be seen that a mask will be placeable in an area defined by the relative spacing of its tongues from one another so that if a short mask has only two tongues which are spaced apart identical to the spacing of the first two slots, then the mask may only be placed in the upper area. Further, in order to assure that registry of the mask is consistent for repetitive usage, one of the openings in the mask for receiving the registration projections may be dimensioned for a close tolerance fit with the pin. In this regard, one or more of the pins may have a shape other than cylindrical to aid in retaining the mask in defined registrable position on the base member.

it can therefore be seen that our invention provides an economical charging easel for electrophotographic printing which may be positioned with respect to a projector and which provides for repeatedly registering a photoconductively coated piece of sheet material with respect to a projected image. The easel has associated therewith a power supply and corona discharge member for electrostatically charging the photoconductive coating while the sheet material is in registry with the optical plane of the image to be projected. Our invention also provides a masking member associated with the easel and registering means for providing an uncharged peripheral portion around the sheet material. Also disclosed is a novel switch mechanism for actuating the corona discharge as well as a preferred embodiment for the easel and transverse arm.

Although the teachings of our invention have herein been discussed with reference to specific theories and embodiments, it is to be understood that these are by way of illustration only and that others may wish to utilize our invention in different designs or applications.

We claim as our invention:

1. For use in an apparatus for accurately replaceably positioning and applying electrostatic charges, a sheet form member having a coating of photoconductive material on at least one face thereof to form a surface to which electrostatic charges are to be repeatedly and successively applied, images exposed and the surface otherwise treated, and said sheet form member having formed therein an asymmetrical array of openings sized and disposed to matingly match with pin registration means with said coating always disposed in the same direction.

2. The combination with the sheet form member of claim 1 of a grounded sheet metal base having an asymmetrical array of upstanding pins therein received in the openings in said sheet form member with the coating thereon disposed on the side away from said base.

3. A device for repeatedly registering a piece of photoconductive sheet material thereon and for applying an electrostatic charge to the sheet material which comprises: a base member having a grounded metal flat surface, registering means projecting from said surface effective to repeatedly position the sheet in the same place on the said surface, said registration means being configured to allow sheet material to be positioned on the said surface in operable position only when the photoconductively coated face of the said sheet material is the side of the sheet material facing the arm, a controlled power source attached to the base member, an arm extending transversely of said base member and slidably mounted thereon through insulating members, the said arm longitudinally movable over a portion of the said surface, means associated with the said arm and operably connected to the said power supply for creating a corona discharge field between the said arm and the said surface when the said power supply is actuated.

4. The device of claim 3 wherein the said registration means comprises a plurality of projecting pins having varying spacing therebetween and the said sheet material has holes therethrough dimensioned to receive the pins, the said holes variously spaced from one another proportionally to the spacing of the said pins whereby the said sheet material can be positioned on the said surface with the said pins projecting through the said holes, the sheet material overlying an operating portion of the said surface only when the photoconductively coated face thereof is remote from the said surface.

5. The device of claim 3 wherein the said registering means includes a plurality of pins projecting from the said surface, the said pins having various configurations, and the said sheet material having holes therein having different configurations corresponding to the configurations of the pins whereby certain pins may be received in certain holes, the said holes positioned on the said sheet material such that the said sheet material can be placed on the said surface with the said pins in registry with the said holes and with the sheet material overlying an operating portion of the said surface only when the photoconductively coated face of the said sheet material is remote from the said surface.

6. The device of claim 3 wherein the said insulating members have anti-friction properties whereby the arm is easily slidable across the said surface, and the said members are positioned adjacent to either end of the arm and spaced from one another with the bottom portion of the arm between the blocks spaced above the said surface.

7. The device of claim 6 wherein the said insulating members are each constructed of a plurality of pieces.

8. The device of claim 6 wherein the base member has projecting tongues along opposite edges and the insulating members have grooves interfitting with the tongues to attach the arm in movable fashion to the base member.

9. The device of claim 3 including a masking member, said masking member defining a rectangular hollow frame, said masking member removably connected to said base member, said masking member dimensioned to overlie marginal portions of the sheet to prevent the same from being charged, and the said masking member cooperating with the registering means to be replaceably positioned in the same spot.

10. The device of claim 9 wherein the same registering means is used to replaceably register both the photoconductively coated sheet material and the masking member.

11. An electrophotographic charging easel comprising a base member, said base member having a metallic grounded flat surface, a plurality of spaced apart registering members projecting from said surface, a trans verse arm member extending transversely across the said base member, a power supply attached to said arm member, insulating blocks attached to said arm member at either end thereof, said insulating blocks slidably mounted on the base member at the transverse sides thereof whereby said arm may he slid longitudinally of the said base member on said insulating blocks, the bottom of said arm between the said insulating blocks spaced from the said surface, and electrical means associated with said arm operatively connected to said power supply for producing a corona discharge electric field between the bottom of said arm and said surface when the power supply is actuated, said base member having a plurality of spaced apart openings extending through the said surface and communicating with cavities under the said surface, a masking member having a plurality of spaced apart tongues along one edge thereof dimensioned to be inserted into the said openings to provide hinge connection between the masking member and the said base member, the said masking member defining a rectangular hollow frame, the said masking member having openings therein dimensioned to receive the said projections, the said projections and openings cooperating to replaceably position the said masking member in a given spot on the said surface, and the said frame adapted to overlie marginal portions of a photoconductive sheet positioned on top of said surface in registry with the said projections to prevent charging of the said portions by the said charging arm.

12. The device of claim 11 wherein the said masking member has an angularly raised portion along the said one edge which when depressed into contact with the said surface will raise the edge opposite the said one edge from the said surface.

13. The ease] of claim 11 wherein the said openings and the said tongues are variably spaced from one another whereby a mask having a given size and a given number of spaced-apart tongues is placeable on the said surface only in one area.

14. The ease] of claim 11 wherein the said tongues are dimensioned and angled with respect to the said masking member so as to retain the said masking member in a hinged open position with the said masking member projecting at an angle from the said surface.

15. The easel of claim 14 wherein the said tongues are dimensioned with respect to the said openings to allow removal of the said mask from the said easel.

16. The easel of claim 11 wherein the said masking member is metallic and is grounded whereby underlying portions of the said sheet material will not be charged when introduced to a corona discharge.

17. A charging easel for electrically charging photoconductively coated sheet material which comprises a base member having U-shaped cross-section top and bottom members positioned in opposition to one another with the side legs thereof at right angles to one another defining end and side walls with longitudinal gaps between the side of the said top member and the side of the said bottom member, the said gaps open to the top, a plurality of spaced-apart projections extending from the top surface of the said base member, the said projections aligned transversely of the said base member and spaced from an end thereof, a plurality of slots in the said top surface aligned longitudinally of the said base member and spaced from a side edge thereof, a transverse arm associated with said base member, said transverse arm having a main body portion supported above the said top surface on insulating glide members at either end thereof, said glide members having grooves therein receiving the side edges of the said top member, said insulating glides extending into the said gaps, a plurality of parallel separated channels open to the bottom extending between said insulating glide members, parallel portions of a corona discharge wire received in said channels, a controlled power supply carried by said transverse arm, said controlled power supply operatively connected to a power cord and to the said corona wire, a switch for activating said power supply in circuit with said power cord and said power supply, indicator lights in circuit with said power cord and said power supply and said switch, one of said indicator lights effective to indicate when power is received by the said power cord and another of said indicator lights effective to indicate when the said power supply is activated, a switch bar mechanism for actuating said switch, said switch bar mechanism actuated by pressure against portions of the said transverse arm, the said transverse arm movable longitudinally across the said base member on the said insulating glides, a hollow rectangular masking member having projecting tangs along one edge thereof, said tangs receivable in the said slots to removably attach the said masking member to the said base, a plurality of openings in the said masking member, said openings indexable with the said projections to accurately, replaceably position the said masking member on the said surface, the said surface being grounded, and means grounding the said masking member and said channels.

18. An electrophotographic charging easel having a base member with a sheet material receiving surface thereon, said surface having a plurality of projections extending therefrom, the said projections serving as registering means for photoconductively coated sheet material having openings therein dimensioned to receive the said projections whereby the said sheet material is replaceably registered on the said surface, a charging member mounted on the said base member, said charging member being movable across at least a portion of said surface, said charging member including a controlled electrical power supply and a switch mechanism for actuating said power supply, said member also including a corona discharge wire having parallel extending portions separated from one another by channel defining members, said portions of the said wire being spaced from said surface and effective to create a corona field between said portions of said wire and said surface, said wire operatively connected to said power source, a metallic masking member detachably connected to the said base member along an edge of the said masking member, said masking member defining a rectangular frame having an open central portion, the said masking member being grounded when in position on the said base member, and means for replaceably registering said masking member a multiplicity of times in the same spot on the said base member.

19. The easel of claim 18 wherein the said charging member includes an indicator means effective to indicate when the said power supply is on.

20. The easel of claim 19 wherein the said charging member includes second indicator means effective to indicate when power is supplied to the said charging member.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 685,895 Dated August 22, 1972 Inventor(s)Joseph E. Wright, Jr. and Donald R. Cohee It is certified that error. appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The first paragraph of the abstract continues as follows:

The device has a grounded flat metal base with pins extending up therefrom in an asymmetrical pattern to fit in complementary holes in photoconductively coated sheet material with a photoconductive surface positioned away from the base. An arm carrying a corona discharge field means is mounted for sliding over the base to charge the photoconductive surface of sheet material positioned on the base.

Col. 4, line 8, change"stop" to --top-- Col. 12, line 6, change 'is to --it- Signed and sealed this 20th day of February 1973.,

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 60376-1 69 U.S. GOVERNMENT PRINTING OFFICE: I969 O-36G-334 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 685,895 Dated August 22, 1972 n (s)Joseph E. Wright, Jr. and Donald R. Cohee It is certified that error. appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The first paragraph of the abstract continues as follows:

The device has a grounded flat metal base with pins extending up therefrom in an asymmetrical pattern to fit in complementary holes in photoconductively coated sheet material with a photoconductive surface positioned away from the base. An arm carrying a corona discharge field means is mounted for sliding over the base to charge the photoconductive surface of sheet material positioned on the base.

Col. 4, line 8, change"stop" to --top- Col. 12, line 6, change "is" to --it-- Signed and sealed this 20th day of February 1973.,

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 60376-5 69 U.S4 GOVERNMENT PRINTING OFFICE I969 O-3$6-334 

1. For use in an apparatus for accurately replaceably positioning and applying electrostatic charges, a sheet form member having a coating of photoconductive material on at least one face thereof to form a surface to Which electrostatic charges are to be repeatedly and successively applied, images exposed and the surface otherwise treated, and said sheet form member having formed therein an asymmetrical array of openings sized and disposed to matingly match with pin registration means with said coating always disposed in the same direction.
 2. The combination with the sheet form member of claim 1 of a grounded sheet metal base having an asymmetrical array of upstanding pins therein received in the openings in said sheet form member with the coating thereon disposed on the side away from said base.
 3. A device for repeatedly registering a piece of photoconductive sheet material thereon and for applying an electrostatic charge to the sheet material which comprises: a base member having a grounded metal flat surface, registering means projecting from said surface effective to repeatedly position the sheet in the same place on the said surface, said registration means being configured to allow sheet material to be positioned on the said surface in operable position only when the photoconductively coated face of the said sheet material is the side of the sheet material facing the arm, a controlled power source attached to the base member, an arm extending transversely of said base member and slidably mounted thereon through insulating members, the said arm longitudinally movable over a portion of the said surface, means associated with the said arm and operably connected to the said power supply for creating a corona discharge field between the said arm and the said surface when the said power supply is actuated.
 4. The device of claim 3 wherein the said registration means comprises a plurality of projecting pins having varying spacing therebetween and the said sheet material has holes therethrough dimensioned to receive the pins, the said holes variously spaced from one another proportionally to the spacing of the said pins whereby the said sheet material can be positioned on the said surface with the said pins projecting through the said holes, the sheet material overlying an operating portion of the said surface only when the photoconductively coated face thereof is remote from the said surface.
 5. The device of claim 3 wherein the said registering means includes a plurality of pins projecting from the said surface, the said pins having various configurations, and the said sheet material having holes therein having different configurations corresponding to the configurations of the pins whereby certain pins may be received in certain holes, the said holes positioned on the said sheet material such that the said sheet material can be placed on the said surface with the said pins in registry with the said holes and with the sheet material overlying an operating portion of the said surface only when the photoconductively coated face of the said sheet material is remote from the said surface.
 6. The device of claim 3 wherein the said insulating members have anti-friction properties whereby the arm is easily slidable across the said surface, and the said members are positioned adjacent to either end of the arm and spaced from one another with the bottom portion of the arm between the blocks spaced above the said surface.
 7. The device of claim 6 wherein the said insulating members are each constructed of a plurality of pieces.
 8. The device of claim 6 wherein the base member has projecting tongues along opposite edges and the insulating members have grooves interfitting with the tongues to attach the arm in movable fashion to the base member.
 9. The device of claim 3 including a masking member, said masking member defining a rectangular hollow frame, said masking member removably connected to said base member, said masking member dimensioned to overlie marginal portions of the sheet to prevent the same from being charged, and the said masking member cooperating with the registering means to be replaceably positioned in the same spot.
 10. The device of claim 9 wherein the samE registering means is used to replaceably register both the photoconductively coated sheet material and the masking member.
 11. An electrophotographic charging easel comprising a base member, said base member having a metallic grounded flat surface, a plurality of spaced apart registering members projecting from said surface, a transverse arm member extending transversely across the said base member, a power supply attached to said arm member, insulating blocks attached to said arm member at either end thereof, said insulating blocks slidably mounted on the base member at the transverse sides thereof whereby said arm may be slid longitudinally of the said base member on said insulating blocks, the bottom of said arm between the said insulating blocks spaced from the said surface, and electrical means associated with said arm operatively connected to said power supply for producing a corona discharge electric field between the bottom of said arm and said surface when the power supply is actuated, said base member having a plurality of spaced apart openings extending through the said surface and communicating with cavities under the said surface, a masking member having a plurality of spaced apart tongues along one edge thereof dimensioned to be inserted into the said openings to provide hinge connection between the masking member and the said base member, the said masking member defining a rectangular hollow frame, the said masking member having openings therein dimensioned to receive the said projections, the said projections and openings cooperating to replaceably position the said masking member in a given spot on the said surface, and the said frame adapted to overlie marginal portions of a photoconductive sheet positioned on top of said surface in registry with the said projections to prevent charging of the said portions by the said charging arm.
 12. The device of claim 11 wherein the said masking member has an angularly raised portion along the said one edge which when depressed into contact with the said surface will raise the edge opposite the said one edge from the said surface.
 13. The easel of claim 11 wherein the said openings and the said tongues are variably spaced from one another whereby a mask having a given size and a given number of spaced-apart tongues is placeable on the said surface only in one area.
 14. The easel of claim 11 wherein the said tongues are dimensioned and angled with respect to the said masking member so as to retain the said masking member in a hinged open position with the said masking member projecting at an angle from the said surface.
 15. The easel of claim 14 wherein the said tongues are dimensioned with respect to the said openings to allow removal of the said mask from the said easel.
 16. The easel of claim 11 wherein the said masking member is metallic and is grounded whereby underlying portions of the said sheet material will not be charged when introduced to a corona discharge.
 17. A charging easel for electrically charging photoconductively coated sheet material which comprises a base member having U-shaped cross-section top and bottom members positioned in opposition to one another with the side legs thereof at right angles to one another defining end and side walls with longitudinal gaps between the side of the said top member and the side of the said bottom member, the said gaps open to the top, a plurality of spaced-apart projections extending from the top surface of the said base member, the said projections aligned transversely of the said base member and spaced from an end thereof, a plurality of slots in the said top surface aligned longitudinally of the said base member and spaced from a side edge thereof, a transverse arm associated with said base member, said transverse arm having a main body portion supported above the said top surface on insulating glide members at either end thereof, said glide members having grooves therein receiving the side edges of the said top member, said insulating Glides extending into the said gaps, a plurality of parallel separated channels open to the bottom extending between said insulating glide members, parallel portions of a corona discharge wire received in said channels, a controlled power supply carried by said transverse arm, said controlled power supply operatively connected to a power cord and to the said corona wire, a switch for activating said power supply in circuit with said power cord and said power supply, indicator lights in circuit with said power cord and said power supply and said switch, one of said indicator lights effective to indicate when power is received by the said power cord and another of said indicator lights effective to indicate when the said power supply is activated, a switch bar mechanism for actuating said switch, said switch bar mechanism actuated by pressure against portions of the said transverse arm, the said transverse arm movable longitudinally across the said base member on the said insulating glides, a hollow rectangular masking member having projecting tangs along one edge thereof, said tangs receivable in the said slots to removably attach the said masking member to the said base, a plurality of openings in the said masking member, said openings indexable with the said projections to accurately, replaceably position the said masking member on the said surface, the said surface being grounded, and means grounding the said masking member and said channels.
 18. An electrophotographic charging easel having a base member with a sheet material receiving surface thereon, said surface having a plurality of projections extending therefrom, the said projections serving as registering means for photoconductively coated sheet material having openings therein dimensioned to receive the said projections whereby the said sheet material is replaceably registered on the said surface, a charging member mounted on the said base member, said charging member being movable across at least a portion of said surface, said charging member including a controlled electrical power supply and a switch mechanism for actuating said power supply, said member also including a corona discharge wire having parallel extending portions separated from one another by channel defining members, said portions of the said wire being spaced from said surface and effective to create a corona field between said portions of said wire and said surface, said wire operatively connected to said power source, a metallic masking member detachably connected to the said base member along an edge of the said masking member, said masking member defining a rectangular frame having an open central portion, the said masking member being grounded when in position on the said base member, and means for replaceably registering said masking member a multiplicity of times in the same spot on the said base member.
 19. The easel of claim 18 wherein the said charging member includes an indicator means effective to indicate when the said power supply is on.
 20. The easel of claim 19 wherein the said charging member includes second indicator means effective to indicate when power is supplied to the said charging member. 